render_utils.py: Add ./ to jinja2 template paths.

This allows us to import and include files located in current directory.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
tests: loaders: New SaveAbort test.

New test that aborts file saving and checks that file was removed and memory
freed.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: BMP, PNM, TIFF: Fix abort path.

* Unlink file if GP_Save{BMP, PNM, TIFF}() was aborted.

* Fix memleak if GP_SaveTIFF() was aborted.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>